Ice Cold Beer Freeplay hack

DogP

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Hey,

Well... I finally got Ice Cold Beer hacked for free play. This one was particularly important because it only allows 9 credits, and it gets a LOT of play. We took one to CGE and I don't think it ever stopped getting play, except when it ran out of credits, and the person didn't know how to coin it up. The one at my house gets a lot of play when people are over as well.

I kinda expected this to be easy, with the exception of having no emulator to use to assist in hacking, and having to burn an EPROM to test any changes. But it turns out that the whole system is an ugly mess, and the code doesn't make it much better :p . I'll admit I don't do much 6809 assembly, but I really don't think the problems stemmed from the language.

But anyway, after looking at just the disassembly and not finding anything particularly useful, I ended up hooking my USB logic analyzer to the 6116 RAM, watching for reads/writes, and since the bus is shared w/ the ROMs, I was able to look a little before it and see what the lower 11 bits of the address are, as well as the data, so I could tell where the code was executing from. Then I determined which address was the credits (and which weren't, including the seperate memory address for the credits display... wtf >_<). So anyway, after logging a bunch of stuff, I went back and modified the code to not decrement the credits when starting the game, as well as always making it think that there's credits while trying to start (and fixed the checksum).

So, the end result is that the display will tell you the actual number of credits, but the start button flashes and starts a game when you press it, even with 0 credits. Nothing else should be affected. You need to burn this to a 27c64, and replace U23. There's no way to turn this on or off... if you want to be able to enable/disable free play, you should burn both the original and the hacked file to a 27c128 and use a switch to toggle between the hacked and unhacked ROM.

Thanks to Scucci for posting the files in the first place, so I could look at the disassembly before actually opening my machine. And attached is a pic of why emulators are great for this stuff :p . Heh, at least I didn't have to lug one of my HP 16500s down there though. ;)

DogP
 

Attachments

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This is really cool!
I'd definately be interested in doing this. Any chance you're offering these modified eproms? I don't have a burner or anything here.
 
This is really cool!
I'd definately be interested in doing this. Any chance you're offering these modified eproms? I don't have a burner or anything here.

I don't feel like selling/shipping them, but I'm sure www.hobbyroms.com would do it for you, if you send them the file. You might want to wait until after this weekend (when it runs all day at my party) to make sure there's no bugs though. I only played a few games (but did make sure I could get all the way to 10), and didn't notice any problems.

DogP
 
What's the chances that this will work with Zeke's Peak as well?

-Tim

I'm not sure... I couldn't find any ROM dumps of ZP. If you dump the ROMs and send them to me, I could tell you, or possibly hack it if it's not much different (I'd assume they're VERY similar code-wise).

DogP
 
I'm not sure... I couldn't find any ROM dumps of ZP. If you dump the ROMs and send them to me, I could tell you, or possibly hack it if it's not much different (I'd assume they're VERY similar code-wise).

DogP

I have no way to do it, or the know-how to do it. But it would be nice.

-Tim
 
Hey,

Well... I finally got Ice Cold Beer hacked for free play. This one was particularly important because it only allows 9 credits, and it gets a LOT of play. We took one to CGE and I don't think it ever stopped getting play, except when it ran out of credits, and the person didn't know how to coin it up. The one at my house gets a lot of play when people are over as well.

I kinda expected this to be easy, with the exception of having no emulator to use to assist in hacking, and having to burn an EPROM to test any changes. But it turns out that the whole system is an ugly mess, and the code doesn't make it much better :p . I'll admit I don't do much 6809 assembly, but I really don't think the problems stemmed from the language.

But anyway, after looking at just the disassembly and not finding anything particularly useful, I ended up hooking my USB logic analyzer to the 6116 RAM, watching for reads/writes, and since the bus is shared w/ the ROMs, I was able to look a little before it and see what the lower 11 bits of the address are, as well as the data, so I could tell where the code was executing from. Then I determined which address was the credits (and which weren't, including the seperate memory address for the credits display... wtf >_<). So anyway, after logging a bunch of stuff, I went back and modified the code to not decrement the credits when starting the game, as well as always making it think that there's credits while trying to start (and fixed the checksum).

So, the end result is that the display will tell you the actual number of credits, but the start button flashes and starts a game when you press it, even with 0 credits. Nothing else should be affected. You need to burn this to a 27c64, and replace U23. There's no way to turn this on or off... if you want to be able to enable/disable free play, you should burn both the original and the hacked file to a 27c128 and use a switch to toggle between the hacked and unhacked ROM.

Thanks to Scucci for posting the files in the first place, so I could look at the disassembly before actually opening my machine. And attached is a pic of why emulators are great for this stuff :p . Heh, at least I didn't have to lug one of my HP 16500s down there though. ;)

DogP

There are two rom files in your zip. I am assuming you only use the freeplay one. The other is the original unmodified file?
 
Seems to work great! Thank you for this!

REQUEST: could it possibly say FREE instead of 'CR 0'? Possible?
 
Yeah, there's an original ROM and the freeplay ROM in the zip. I did that in case someone wanted to double them up on a 27c128.

REQUEST: could it possibly say FREE instead of 'CR 0'? Possible?

That may be possible, but:
a) I wanted to get this done as quickly as possible, since I've still got at least 3 other freeplay hacks I'm trying to get done before Saturday's party (so I'm just getting the bare minimum for now).

b) The display is controlled by an Intel 8279, so I'd need to spend a few minutes to see exactly how to do that, and hope that there's room in the ROM to squeeze it in there.

c) If I do revisit this, I plan on making it actually go through the attract mode (with the blinking lights) rather than just waiting for start. I could possibly add FREE to the display when it shows credits though.

d) Without an emulator, all of this would likely be pretty tedious to accomplish.

DogP
 
Yeah, there's an original ROM and the freeplay ROM in the zip. I did that in case someone wanted to double them up on a 27c128.



That may be possible, but:
a) I wanted to get this done as quickly as possible, since I've still got at least 3 other freeplay hacks I'm trying to get done before Saturday's party (so I'm just getting the bare minimum for now).

b) The display is controlled by an Intel 8279, so I'd need to spend a few minutes to see exactly how to do that, and hope that there's room in the ROM to squeeze it in there.

c) If I do revisit this, I plan on making it actually go through the attract mode (with the blinking lights) rather than just waiting for start. I could possibly add FREE to the display when it shows credits though.

d) Without an emulator, all of this would likely be pretty tedious to accomplish.

DogP

So, this removes the attract??
 
Yeah, it doesn't go through the flashing lights and scroll ICE COLD BEER or whatever it normally does... it just sits there flashing the start button and whatever it does when you have credits. At least I believe so... it was pretty late when I was messing with it, and all I really cared about was that it didn't require the coin switch to be pressed :p .

DogP
 
Im pretty sure I have the ZP rom dumps on my pc in the shop. PM me if you want them.

EDIT: Yes I have them. Just pulled them off my other pc, here they are.
 
Last edited:
Cool... thanks for posting them. From a quick look, it seems that they're similar, but certainly different. I'll take a look at them sometime and see if the same hack can be applied.

DogP
 
I just looked at the code, and modified it how I think it needs to be. I'll burn them tomorrow and test it out.

DogP
 
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